The present invention relates to a data filing system and, more particularly, to a computer-controlled filing system for efficiently filing data such as design drawings, documents, and the like, and retrieving desired data, as required.
In recent years, an electronic filing system for storing a large volume of data in office, such as drawings, documents, and the like, in a large-capacity data storage unit has been developed. In a system of this type, various types of documents can be efficiently filed in accordance with the memory capacity of the data storage unit, and a desired document can be searched for and extracted by an operator under the control of a computer, as needed. In general, an appropriate identification code or codes are added to an input document as a management code, and in a document retrieving mode, the required document is searched for, from among the large volume of stored document data, in accordance with the code.
In a data-filing system with the conventional arrangement, although the data-filing/retrieving operation can be efficiently performed at high speed, it is performed on the basis of the above-mentioned management code and can therefore be performed only in units of documents. For example, a desired drawing (such as a circuit diagram) can be extracted from among a large volume of stored drawing data. However, it is difficult to directly retrieve only part of a drawing, such as a symbol or mark of a given drawing (e.g., a unit circuit serving a predetermined function, such as an AND gate). This is because the filing system does not "understand" the content of storage documents. If the system were capable of understanding the contents of the storage drawings in the same way as the human brain, it would not be so difficult to specify, in which portion of which drawing a desired circuit is included, with certain accuracy under any retrieval condition. In the data-filing system, as long as the document filing/retrieving operation is performed based on the management code corresponding to a specific document, the above-mentioned flexible mode retrieval cannot be performed.
If a recently developed automatic pattern recognition technique is applied, the data filing/retrieving operation can be performed in a flexible manner as mentioned above. In this case, the pattern feature of a paper document of an input drawing is automatically recognized (pattern-recognized), and is electronically coded. As a result, storage data can be compressed and stored at high level, and desired partial image data can be directly retrieved.
With such an intelligent data-filing system, however, it is an important technical problem to render storage data compact and improve operating speed. With the advance and growth in complexity of the automatic pattern recognition technique, recognition performance and precision have been improved. If a pattern recognition processing function is provided in a filing system, the pattern feature of an input paper document can be automatically recognized in the system, and a partial figure pattern can be converted to a simple recognition code. For example, when the pattern feature of each unit circuit (e.g., an AND gate) constituting a circuit drawn on a circuit diagram is pattern recognized, the content of the paper document is converted to an electronic code of several digits. Then, the data volume necessary for representing an identical information volume can be greatly decreased and hence the total storage data can be rendered compact. Therefore, drawing data to be stored in the filing system can be compressed to a higher level, and the final storage data can be rendered compact. However, a great deal of time is required to compress image data to a high level. This is because, in order to obtain highly compressed data, various data compression processing operations must be repetitively and sequentially executed for each image pattern. Therefore, in a current intelligent data-filing system, the conflicting requirements of compact storage data and high operating speed of data compression processing cannot be satisfied at the same time.